Novel method of electrodeposition

ABSTRACT

A novel method of preparing and using an improved electrolyte bath for the purpose of electrodeposition of metallic film onto a substrate is disclosed. The electrolyte bath makes use of unexpected findings in the process of electrodeposition with the claimed compounds and elements to perform the process with less expensive and more environmentally-friendly materials to produce a consistent, high-quality deposition.

CROSS-REFERENCE TO RELATED APPLICATIONS

This nonprovisional patent application relates back to and claims the benefit of provisional application No. 63/265,931. The contents of the disclosure therein are incorporated by reference as though fully set forth herein.

BACKGROUND

Known processes for stable electrodeposition of thin film material onto an electrically conductive substrate use an electrolyte bath; however, these processes have several problems known in the art. Among these are inconsistencies in coverage of the substrate, irregularities in the thickness of the film, delamination of the film layer or layers, pitting, flaking, stretching, and variation in concentration. These problems hinder attempts to scale up the electrodeposition process. Moreover, the processes themselves are known to require wasteful volumes of environmentally unfriendly compounds. The processes themselves are necessary for the production of flexible, thin-film electromagnetic materials with high hesitivity, meaning materials with a high peak value of magnetic conductivity in the permeability spectrum. A need exists within the art for a process of electrodeposition which reduces or eliminates these problems.

SUMMARY OF THE INVENTION

The method claimed herein is an improved method for electroplating of high-hesitivity film onto an electrically conductive substrate. The chemistry of the method, along with certain techniques disclosed herein, address several long-felt needs in the art and produce results that would not have previously been expected.

The method presented may be described herein in terms of functional black components and various processing steps. These functional blocks may be realized through utilizing the method in any number of custom or off-the-shelf components configured to perform the specified tasks in order to accomplish the method and achieve the desired results. The methods and systems described herein are exemplary and illustrative of the best mode; such examples are not, intended to otherwise limit the scope of the present invention, and the methods and systems may be practiced in other applications and with other tools or materials meant for continuous electroplating of electrically conductive materials onto an electrically conductive substrate; such methods may be apparent to one skilled in the art in light of the present disclosure and are intended to be claimed herein. For the sake of brevity, conventional steps in the functional aspects of this method may not be set forth in detail.

In its preferred embodiment, the method produces components for conformal magneto-dielectric antennas with high hesitivity. Magneto-dielectric dipole antennas, including conformal antennas useful in applications in which a large antenna body is undesirable, radiation efficiency of the antenna is proportional to hesitivity. In other words, higher hesitivity materials are desired for the higher performance in this and other fields.

Other applications for the present methods may become apparent to one skilled in the art in light of this disclosure and are intended to be claimed herein; for example, the deposition of electroconductive film is useful in the production of solar panels.

Certain steps of the process below may be omitted or modified. Provided such modifications and omissions are consistent with the claims, such modifications are intended to be included with the disclosures and claims herein.

In the art, the process for electroplating of one or more depositants, namely, electrically conductive materials onto a substrate to form a thin film magnetic material with high hesitivity will typically incorporate the steps of passing a substrate through an electrolyte bath comprising various metals, the substrate being subject to a magnetic field during deposition in order to produce the layering of the film onto the substrate. Most commonly used for the film is permalloy, a magnetically permeable nickel-iron alloy typically comprising 80% nickel and 20% iron. The present disclosure includes in an enabling disclosure of the preferred embodiment of the method for the layering of permalloy; the method may be generalized to other applications of the disclosed systems and methods. Other applications contemplated herein include but are not limited to use of the method for electrodeposition of doped nickel, in which nickel is doped with cobalt or other elements from the cobalt group, or with elements from the copper group, as well as iron or elements from the iron groups doped with elements from the cobalt group or from the manganese group.

In various applications of the method, the layered magnetic material is preferably between 20 nanometers (nm) and 350 nm in thickness to retain high hesitivity. At thicknesses above 350 nm, the material may experience a decrease in hesitivity. At thicknesses below 20 nm, measurements of hesitivity may be unreliable. Indeed, thinner layers are known to have higher hesitivity, but are less stable and more difficult to manufacture; it is desirable to maintain high hesitivity with thicker layers of magnetic material. However, thicker layers are also more subject to delamination as they are exposed to the electrolyte bath for longer.

Within the primary intended application of creating low-profile and conformal magneto-dielectric antennas, various antenna geometries and profiles may have a bandwidth in the range of approximately 900 MHz to 4 GHz, reaching the limits of the ultra-high frequency (UHF) band and the lower ranges of the super-high frequency (SHF) band, useful for transmission and receiving devices in the communications industry, particularly for military and security applications. Antennas produced with embodiments of the method comprising cobalt-doped iron may have higher resonance frequencies.

Another benefit of the method disclosed herein is the use of smaller quantities of less expensive and less environmentally damaging materials. Cyanides, sulfates, and sulfuric acids are commonly used. Such materials can be dangerous to handle and store, and are expensive to properly dispose of. The industries using known methods have long felt the need for a less expensive, less dangerous, less polluting method. The method disclosed herein fulfills that need through the previously unexpected results of the use of alternative compounds.

DESCRIPTION OF THE DRAWINGS

A more complete understanding of the present technology may be derived by referring to the detailed description in connection with the following figures. Like reference numbers refer to similar elements and steps throughout the figures.

Elements and steps are illustrated for simplicity and clarity and have not necessarily been rendered according to any particular embodiment, sequence, or scale. The figures are for illustrational purposes only and are not intended to limit the scope of the present disclosure. Various aspects of the present technology may be more fully understood from the detailed description and the accompanying drawings.

FIG. 1 is a detail view of the first roller, in which a length of substrate can be seen entering the bath chamber. This image contains a view of the preferred sheathed copper wire.

FIG. 2 is a detail view of the bath chamber where the substrate enters through the feeding connection 301. The electrolyte bath can be seen within the electrolyte basin, as can the electrical anode.

FIG. 3 is a broader view of the bath chamber. The substrate can be seen submerged within the electrolyte bath inside of the electrolyte basin. This image contains the preferred reference electrode to enable use of the optional potentiostat.

FIG. 4 is a detail view of the second roller in which the substrate is visible after passing through the bath chamber, rinsing chamber, and drying chamber.

FIG. 5 is a view of the overall apparatus used in the method. The optional recirculatory and reserve tank are visible.

DETAILED DESCRIPTION OF THE INVENTION

The first part of the method comprises assembling the apparatus. Other than those exceptions set forth herein, an electrolyte bath 302 for electrodeposition onto a substrate 100 are known in the art and need not be reproduced in excessive detail herein; except where noted, description of the apparatus is for illustrative purposes and to establish necessary primary antecedent basis.

The apparatus must be assembled to comprise a bath chamber, at least two rollers, said rollers each further comprising at least one working electrode, a rinsing chamber 400, and a drying chamber 500. A recirculator is preferably assembled as part of the apparatus; said recirculator further comprising a reserve tank 310. The rollers must be configured to feed a substrate 100 from a first roller 210 to a second roller 220, in such a way that as to pass through the bath chamber, rinsing chamber 400, and drying chamber 500. Other components and chambers may be added to the apparatus according to techniques known in the art.

A first roller 210 of the at least two rollers is assembled, comprising a first working electrode 211.

The bath chamber is preferably assembled to comprise an electrolyte basin 305, an electrical anode 304 configured for submergence within the electrolyte basin 305, a feeding connection 301 to the first of the at least two rollers, and preferably a recirculating connection to the recirculator. The bath chamber may further comprise a potentiostat and a reference electrode 306 in alternative embodiments of the present invention.

The rinsing chamber 400 is assembled on one side of the bath chamber, preferably to the opposite side of the first roller 210 in relation to the bath chamber, and is assembled to comprise a feeding connection 301 to the bath chamber, at least one rinsing sprayer, said at least one rinsing sprayer being preferably configured to spray water, and a drain.

The drying chamber 500 is assembled on one side of the rinsing chamber 400, preferably to the opposite side of the rinsing chamber 400 in relation to the bath chamber, and is assembled to comprise a feeding connection 301 to the rinsing chamber 400 and at least one blower, said at least one blower being preferably configured for use of inert gas.

A second roller 220 of the at least two rollers is assembled, preferably to the opposite side of the drying chamber 500 in relation to the rinsing chamber 400, and is assembled to comprise a feeding connection 301 to the drying chamber 500. In the preferred embodiment, the working electrode 211 on the first roller 210 and the working electrode 221 on the second roller 220 are electrically connected by a roller conductor 212, said roller conductor being preferably a sheathed copper wire; in alternative embodiments, the roller conductor may be a copper rod or other electrically conductive material connection.

A recirculator is preferably assembled, said recirculator being configured such that the reserve tank 310 is connected by recirculating connection to the bath chamber.

The apparatus should further preferably be prepared to comprise a water supply and an electrical power supply. Water supplies and power supply are well known in the art and need not be expounded upon further.

The method next comprises the step of preparing an electrolyte bath 302. The electrolyte bath 302 first comprises a liquid polar solvent, typically and preferably distilled water, in which certain compounds are dissolved for the electrodeposition process. For the preferred embodiment of permalloy deposition on a copper substrate 100, the further additive steps described below may be performed in any order. Other embodiments may be sensitive to the order in which additives are dissolved.

At least one depositant is prepared, each of the at least one depositants being an ion salt bonded to a metal or another electrically conductive material which it is desired should be bound to the substrate 100. The at least one depositants are dissolved within the liquid polar solvent for deposition; other compounds comprise additives to affect the process of electrodeposition of the depositant from the onto a substrate 100 while separating the depositant from the ion salt. The electrolyte bath 302's composition changes over the course of both the present method and those methods already known in the art as depositant and ion salts are broken down and depositants are deposited on the substrate 100 while the ion salts and any resulting byproducts remain in the solution; the method naturally must account for this change over time in order to maintain consistent, high-quality deposition of an electroconductive film onto the substrate 100.

In the preferred embodiment for depositing permalloy, the depositant and ion salts may comprise iron chlorides, iron sulfates, nickel chlorides, nickel sulfates, nickel chloride hexahydrates, and other ion salts known in the art. Additional embodiments may comprise doped metal compounds such as iron doped with cobalt, or other variations known in the art. In the state of the art, chloride salts are known to be more stable and result in higher-quality electroplating deposition than sulfate salts. However, the preferred embodiment disclosed and enabled herein has demonstrated in experimental results the unexpected outcome of no significant difference in the performance of sulfate or chloride salts. Consequently, an electrolyte bath 302 primarily comprising less expensive nickel sulfates and iron sulfates are preferred, but not required.

In the preferred embodiments for electrodeposition of permalloy, the electrolyte bath 302 should begin the method at concentrations of iron (II) sulfate from 2 to 3 g/L, nickel (II) sulfate hexahydrate from 50 to 60 g/L and preferably 55 g/L, and nickel (II) chloride hexahydrate from 6 to 7 g/L. Other concentrations may become apparent to one skilled in the art in light of this disclosure; such embodiments are intended to be claimed herein.

The method step in preparation of the electrolyte bath 302 further comprises the step of adding additives.

A first additive, saccharin (C₇H₅NO₃S), a common artificial sweetener used in the electroplating industry as a material stress reducer, is added to the electrolyte bath 302 solution. Saccharin decreases tension and material stresses within the electroconductive film, resulting in the increased uniformity of deposition. Experimental results suggest that in the preferred embodiment, the electrolyte bath 302 should contain a concentration of 0.27 g/L of saccharin for permalloy production; other concentrations may be used, and other concentrations may be preferred for different types of electroconductive films. However, overconcentration of saccharin appears to lose the beneficial effect and instead interfere with proper electrodeposition, resulting in lower hesitivity. Concentrations as high as 1 g/L are useful for permalloy deposition, but no higher.

A second additive to the electrolyte bath 302 comprises L-ascorbic acid, more commonly known as vitamin C. L-ascorbic acid acts as an anti-oxidation agent which improves the chemical stability of iron in the electrolyte bath 302 solution, reducing the impact on undo/nifty of electroconductive film deposition caused formation of iron hydroxide. Experimental results show a concentration between 5 g/L and 5.28 g/L is ideal for the preferred embodiment of permalloy electrodeposition; other concentrations close to this value may be used.

A third additive, boric acid, is added to the electrolyte bath 302. Boric acid is used in the art to maintain a consistent pH value in the electrolyte bath 302, preferably at a pH of 3, which is between that typical of orange juice and vinegar. A stable pH value is preferable in order to maintain consistency in the properties of the electrolyte bath 302, which in turn improves the consistency of the electroconductive film. Boric acid concentrations of 10 g/L are preferred with this method in the preferred embodiment of permalloy deposition. Boric acid at this preferred concentration causes the deposited permalloy to have a noticeably shinier, more reflective appearance which corresponds with and visually indicates the desired higher hesitivity. Other concentrations between 1.33 g/L and 25 g/L yield usable results, but the preferred embodiment remains 10 g/L.

A fourth additive, sodium dodecyl sulfate (SDS), is added to the electrolyte bath 302. Used in the preferred embodiment of the method, SDS acts as a surfactant, decreasing interfacial tension between the electrodeposited compound and the substrate 100 as well as reducing the stress in the electroconductive film, preventing delamination and deformation. In the preferred embodiment, a concentration of 1 g/L of SDS is used.

Notably, the method claimed herein does not require the use of certain compounds commonly used in an electrolyte bath 302. Ammonium chloride (NH₄Cl) may be omitted. In the art, ammonium chloride is generally considered one of the most important elements in an electrolyte bath 302 for its effects as a supporting electrolyte and as a pH buffer. Similarly, Dimethylamino-benzaldehyde (DMAB) may be omitted as well. DMAB is a commonly used reducing agent. The elimination of these compounds from the known processes both reduces the expense of electrodeposition and reduces the harmful waste produced.

The final, preferred bath chemistry for the preferred embodiment of the method used for electrodeposition of permalloy onto a copper substrate 100 is between 2 and 3 g/L of Iron (II) Sulfate, between 50 and 60 g/L of Nickel (II) sulfate, 5.28 g/L of L-ascorbic acid, 10 g/L of boric acid, 1 g/l of SDS, and 0.27 g/L of saccharin. It is further desirable to substitute in place of the nickel (II) sulfate a blend of nickel (II) sulfate at 48.63 g/L and nickel (II) chloride at 0.99 g/L. Further embodiments of the present invention may use varying ratios of these compounds.

The method next comprises the steps of preparing a substrate 100. The substrate 100 is attached to the first roller 210, passed through the feeding connection 301 first to the bath chamber, then to the rinsing chamber 400, then to the drying chamber 500, and finally to the second roller 220. The substrate 100 should be placed in such a manner that it is not in direct contact with the electrical anode 304.

The method next comprises the step of electrodeposition. The electrolyte basin 305 is filled with the electrolyte bath 302 such that the electrical anode 304 is at least partially submerged and the substrate 100 is at least partially and preferably entirely submerged. An operator performing the method should keep the electrolyte bath 302 at a consistent level and chemical consistency, preferably by using the recirculator to circulate the electrolyte bath 302 between the electrolyte basin 305 and the reserve tank 310; other methods are possible, such as directly pouring additional quantities of electrolyte bath 302 into the electrolyte basin 305.

Electrical current is passed between the working electrodes, the substrate 100, and the electrical anode 304. Ideally, the current density, as a quantity of electrical current per unit surface area of the substrate 100, is kept at 2.5 mA per square centimeter; current density as low as 2 mA per square centimeter and as high as 3 mA per square centimeter may also be used.

The at least two rollers are activated to pass substrate 100 from the first roller 210 to the second roller 220 through the apparatus. The rate of rotation of the at least two rollers may be varied in order to change the time the substrate 100 is exposed to the electrolyte bath 302. As the substrate 100 is exposed to the electrolyte bath 302 and the electrical current, depositants bonded with ion salts react with the substrate 100 to separate ions salts from the depositants; depositants adhere to the substrate 100 as an electroconductive film. For the preferred embodiment of permalloy deposition onto copper, an exposure time of five hundred seconds is preferred. Lower exposure times will reduce overall thickness of deposited electroconductive film; higher exposure times will increase overall thickness of deposited electroconductive film.

Optionally and preferably, the substrate 100 may be replaced on the first roller 210 and the step of electrodeposition repeated in order to deposit additional layers of electroconductive film on the substrate 100 until a desired electroconductive film thickness is obtained. This step enables a thicker deposition of electroconductive film on the substrate 100 with less risk of delamination caused by prolonged exposure of the substrate 100 to the electrolyte bath 302.

The electroconductive film may be layered in order to produce a thicker deposition over the substrate 100. Thicker layers are typically known in the art to have decreased hesitivity, but thinner layers are more difficult to keep consistent. In the preferred permalloy deposition embodiment, the method may be employed to produce conformal antennas with an electroconductive film thickness of between two nanometers and three-hundred fifty nanometers, but preferably either a single layer one-hundred fifty nanometers thick or three layers fifty nanometers thick, having an antenna bandwidth of approximately 900 MHz to approximately 4 GHz, desirable for security and military applications. Alternate embodiments of cobalt-doped iron or permalloy may have lower bandwidths between 50 MHz and 300 MHz.

The present invention has been described with reference to an exemplary embodiment. Changes and modifications may be made to the exemplary embodiment without departing from the scope of the present technology. These and other changes or modifications are intended to be included within the scope of the present invention. 

What is claimed is:
 1. A method for electroplating a depositant onto a substrate via electrochemical deposition, the method comprising the following steps: Preparing an apparatus for the method, said apparatus comprising a bath chamber, at least two rollers, a rinsing chamber, and a drying chamber; In which the at least two rollers comprise a first roller and a second rolling, each further comprising working electrodes; In which the bath chamber further comprises an electrolyte basin, an electrical anode, and a feeding connection to the first roller; In which the rinsing chamber comprises a feeding connection to the bath chamber, at least one rinsing sprayer, and a drain; In which the drying chamber comprises a feeding connection to the rinsing chamber and at least one blower; In which the container is configured to contain the electrolyte bath and to pass the substrate from one of the at least two rollers to a second of the at least two rollers while submerging the substrate in the electrolyte bath; Preparing an electrolyte bath, said electrolyte bath comprising a solution in a liquid polar solvent in which is dissolved a quantity of L-ascorbic acid, a quantity of saccharin, a quantity of SDS, a quantity of boric acid and at least one depositant, said depositant being bonded to an ion salt; Preparing materials for the method, said materials comprising an electrically conductive substrate, by attaching the substrate to the first roller, passing the substrate through the bath chamber, rinsing chamber, and drying chamber to the second roller; Filing the electrolyte basin with the electrolyte bath such that the substrate and the electrical anode are at least partially submerged; Causing the rollers to rotate so as to pass the substrate through the electrolyte bath at a certain speed; Directing an electrical current between the working electrodes and the electrical anode, such that the reaction of the electrolyte bath, the substrate, the electrical current, and the depositant causes an electroconductive film to be deposited on the substrate; Spraying the substrate with a quantity of water as the substrate passes through the rinsing chamber; and Drying the substrate as it passes through the drying chamber.
 2. The method of claim 1, in which the liquid polar solvent is water.
 3. The method of claim 1, in which the boric is dissolved in a density of between 1 and 25 g/L.
 4. The method of claim 1, in which the L-ascorbic acid is dissolved in a density of up to 1 g/L.
 5. The method of claim 1, in which the SDS is dissolved in a density of up to 2 g/L.
 6. The method of claim 1, in which the saccharin is dissolved in a density of up to 1 g/L.
 7. The method of claim 1, in which the step of passing electrical current between the working electrodes and the electrical anode comprises the step of limiting the electrical current to a current density of between 2 and 3 mA per square inch of the substrate.
 8. The method of claim 1, in which the apparatus further comprises a recirculatory, said recirculatory further comprising a reserve tank and a recirculating connection connected to the electrolyte basin; In which the additional step of controlling the depth and composition of the electrolyte basin by circulating the electrolyte bath between the reserve tank and the electrolyte basin is performed during, the step of passing the substrate through the apparatus.
 9. The method of claim 1, in which the blower is configured to blow an inert gas to dry the substrate.
 10. The method of claim 1, in which the at least one depositant comprises nickel sulfate at a density of between 40 and 60 g/L and iron sulfate at a density of between 2 and 3 g/L, and in which the method results in an electroconductive film which is permalloy.
 11. The method of claim 10, in which the iron sulfate is doped with at least one element from the cobalt group.
 12. The method of claim 1, in which the method is employed to create high-hesitivity antennas.
 13. An electrolyte bath for use in electrodeposition of one or more depositants onto a substrate, said electrolyte bath comprising: A liquid polar solvent in which is dissolved L-ascorbic acid, boric acid, saccharin, and SDS; In which the one or more depositants are further dissolved; Such that the one or more depositants will tend to adhere to the substrate as an electroconductive film when an electrical current is passed between one or more working electrodes and an electrical anode when the substrate and electrical anode are submerged within the electrolyte bath.
 14. The electrolyte bath of claim 13, in which the liquid polar solvent is water
 15. The electrolyte bath of claim 13, in which the boric is dissolved in a density of between 1 and 25 g/L.
 16. The electrolyte bath of claim 13, in which the L-ascorbic acid is dissolved in a density of up to 1 g/L.
 17. The electrolyte bath of claim 13, in which the SDS is dissolved in a density of up to 2 g/L.
 18. The electrolyte bath of claim 13, in which the saccharin is dissolved in a density of up to 1 g/L.
 19. The electrolyte bath of claim 13, in which the electrical current has a current density of between 2 and 3 mA per square inch of the substrate
 20. The electrolyte bath of claim 13, in which the at least one depositant comprises two depositants, namely nickel sulfate at a density of between 40 and 60 g/L and iron sulfate at a density of between 2 and 3 g/L, such that the electroconductive film is permalloy. 